Hitherto, various kinds of layer-forming techniques have been used in the cases of the formation of plural layers constituting semiconductors or semiconductor materials. Representative examples of these layer-forming techniques may include, e.g., vacuum evaporation processes, sputtering processes, and CVD (chemical vapor deposition) processes. Among these layer-forming techniques, the CVD process has certain characteristics such that it can provide a high film-forming deposition rate for the layer formation, and it can accomplish the film formation within a relatively short period. Accordingly, the CVD process has been used for many steps in the production of various kinds of materials for electronic devices or semiconductors such as MOS-type semiconductor devices.
In general, the production process according to the present invention is widely applicable to the production of materials for electronic devices. For the convenience of explanation, however, the background art relating to an EPROM, an embodiment of the nonvolatile memory called “flash memory”, will be described here.
EPROM has, for example a multi-layer structure as shown in. FIG. 12.
Referring to FIG. 12, the multi-layer structure of the EPROM comprises: a substrate 100 to be processed comprising p-type single-crystal silicon; a multi-layer structure disposed on the substrate 100, wherein an insulating layer 101 of SiO2, and semiconductor layers 102 and 103 of polycrystal silicon are alternatively stacked while forming predetermined patterns; and a metal layer 104 of a metal (aluminum, copper, etc.) disposed on the multi-layer structure.
In such a semiconductor device, the above-mentioned CVD process is widely used for forming the semiconductor layers 102 and 103 of polycrystal silicon, and the interlayer SiO2 layers disposed therebetween.
However, in the layers formed by the CVD process, the resultant surface roughness, and defects in the film are relatively noticeable, and the valences of atomic bonding called “dangling bonds” are liable to be formed so that the dangling bonds are directed toward the inside of the film. When these dangling bonds are formed so that they are directed toward the inside of the film, the dangling bonds can affect the flows of electrons in this layer and other adjacent layers. As a result, there can occur a problem such that electric characteristics of the layer can be deteriorated, and the quality of the resultant electronic device per se can be deteriorated accordingly.